MC68HC05X16 Datasheet, PDF (58/232 Pages) Freescale Semiconductor, Inc – High-density complementary metal oxide semiconductor HCMOS) microcontroller unit

Freescale Semiconductor, Inc.
4.4
Port D
This 8-bit input-only port shares its pins with the A/D converter subsystem. When the A/D
converter is enabled, pins PD0-PD7 read the eight analog inputs to the A/D converter. Port D can
be read at any time, however, if it is read during an A/D conversion sequence noise, may be
injected on the analog inputs, resulting in reduced accuracy of the A/D. Furthermore, performing
a digital read of port D with levels other than V_DD or V_SS on the port D pins will result in greater
power dissipation during the read cycle.
4
As port D is an input-only port there is no DDR associated with it. Also, at power up or external
reset, the A/D converter is disabled, thus the port is configured as a standard input-only port.
Note:
It is recommended that all unused input ports and I/O ports be tied to an appropriate
logic level (i.e. either V_DD or V_SS).
4.5
Port registers
The following sections explain in detail the individual bits in the data and control registers
associated with the ports.
4.5.1 Port data registers A and B (PORTA and PORTB)
Port A data (PORTA)
Port B data (PORTB)
Address bit 7
bit 6
bit 5
bit 4
bit 3
bit 2
bit 1
bit 0
State
on reset
$0000
Undefined
$0001
Undefined
Each bit can be configured as input or output via the corresponding data direction bit in the port
data direction register (DDRx).
The state of the port data registers following reset is not defined.
INPUT/OUTPUT PORTS
MC68HC05X16
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Rev. 1
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